Characterizing Lenslet Arrays for

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Characterizing Lenslet Arrays for the Keck
Adaptive Optics System Laboratory for Adaptive
optics (LAO) UC Santa Cruz Name Abubakarr
Bah Home Institution Santa Rosa Junior
College Advisor Dr. Don Gavel Mentor Dr. Renate
Kupke
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What are Lenslets?

• Small lenses (50 um- 1 mm)
• Part of an array.
• Found in Shack-Hartmann wave front sensors.

Lenslet on a Shack-Hartmann wavefront sensor
Image taken from http//www.ctio.noao.edu
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My Project Information

• Characterizing Lenslets arrays for
• the Keck adaptive optics system
• Focal Length
• Pitch Measurement
• Transmission
• Lenslet Optical Figure

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Focal length setup
Pinhole (5 µ)
Aperture
Lenslet
.633 um
CCD
Computer
f
Microscope Objective (50x)
Microscope Objective (10x)
Diode laser
Collimated light
Hartmann Spots
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Focal length at a single wavelength (.633 um)
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Focal length set up for different Wavelength.
Microscope Objective (50x)
Filter
CCD
Computer
White light Source
Microscope Objective (10x)
Lenslet
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Focal length at diff. wavelength
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Pitch Measurements

• Spot Pitch Measurements
• - Same as Focal Length Setup
• - Distance b/w Spots

• Pitch Measurements
• - LAO's Olympus microscope
• - 20 Lenslet at a time

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Focal Spot Pitch
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Pitch Measurements Using the LAO's Olympus
microscope Measurements were taking 20 lenslet at
time
up towards lenslet III Right towards markings.
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Transmission of the Lenslets
Keck Specification gt97
EXPERIMENTS

• Used The UCO Lick Optical Shop's
• spectrophotometer.
• Made a simple optical setup

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Throughput.
Filter
Lenslet
Pin Hole
White light Source
Photometer
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Transmission of Lenslet
Max 1.00
Min 0.84
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Lenslets optical Figure
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Conclusions
. Focal length and Pitch meet specifications .Tran
smission meets the specifications within
500-950 nm . Lenslet has a parabolic shape and
steps patterns (surprising observation !)
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Acknowledgments
Dr. Don Gavel Dr. Renate Kupke Sandrine
Thomas Daren Dillon Marco Reinig Members of the
LAO lab Center for Adaptive Optics (CFAO)
This work has been supported by the National
Science Foundation Science and Technology Center
for Adaptive Optics, managed by the University of
California at Santa Cruz under cooperative
agreement No. AST - 9876783."